Fix: Add explicit CORS headers and improve file serving for report-demo route

Fix: Add test route and improve report-demo route with better error handling

Fix: Improve report-demo route with better path resolution and error handling

Add /report-demo route to serve HTML report template

feat: add report-template.html static hosting

email-done

🔧 Fix OAuth: auto-detect redirect_uri + sync all ClassLens updates

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Add unmanged sample with a minimal backend (#98)